In current actuators, the on/off operation in a pneumatic device is achieved with an electric solenoid valve. Vacuum force is applied to the actuator only when the solenoid is “on” and only when the vacuum force is high enough to move the actuator the full length of its travel. Alternately, without a solenoid controlling the actuator's exposure to vacuum, an actuator exposed to vacuum force under all conditions will “float” between the on position and the off position. Floating is undesirable, inefficient, and provides poor control of the device attached to the actuator.
Often, solenoid actuated valves are spring biased to a default condition and require the application of current to a coil to move the valve to the energized position. However, as long as the valve is in the on-state, then it is to be appreciated that power is consumed. Thus, there is a need in the art for energy efficient actuators that are effective at controlling an electric solenoid's on-state, while reducing the amount of power consumed.